Base vaccines shown to be less effective against the omicron variant

Pfizer and AstraZeneca’s COVID-19 vaccines are not as effective in fighting off the omicron variant, but researchers say a booster shot will improve immunity.

Researchers at the University of Oxford tested blood samples of people 28 days after their second dose of either vaccine. When omicron was introduced to those samples, scientists reported a substantial decrease in antibodies compared to the immune responses seen against earlier variants. However, the report noted that after a booster dose vaccines were thought to be 70 to 75 percent effective at preventing symptomatic infections.

The most common side effects reported after getting a third shot of an MRNA vaccine, like Pfizer or Moderna, were pain at the injection site, fatigue, muscle pain, headache and fever followed by chills and nausea.

Overall, the CDC says that so far, reactions reported after getting a booster shot were similar to those after the two-dose or single-dose primary series.